HONG KONG — The Chinese government is shutting down the mobile service of residents in Xinjiang who use software that lets them circumvent Internet filters, escalating an already aggressive electronic surveillance strategy in the country’s fractious western territory.

Starting last week, shortly afterterrorist attacks in Paris, the local police began cutting the service of people who had downloaded foreign messaging services and other software, according to five people affected.

The people, who spoke on the condition of anonymity over concerns about retaliation from local security forces for speaking to foreign news media, all said their telecommunications provider had told them to go to a local police station to have service restored.

“Due to police notice, we will shut down your cellphone number within the next two hours in accordance with the law,” read a text message received by one of the people, who lives in the regional capital of Urumqi. “If you have any questions, please consult the cyberpolice affiliated with the police station in your vicinity as soon as possible.”